This subproject is one of many research subprojects utilizing the resources provided by a Center grant funded by NIH/NCRR. The subproject and investigator (PI) may have received primary funding from another NIH source, and thus could be represented in other CRISP entries. The institution listed is for the Center, which is not necessarily the institution for the investigator. Adolescent hyperandrogenemia appears to be a precursor to adult polycystic ovary syndrome (PCOS). We have found that adult women with PCOS have a reduced sensitivity to progesterone inhibition of GnRH pulsatility. We propose to examine progesterone inhibition of GnRH pulsatility in normal and hyperandrogenemic adolescent girls to determine whether this may be an underlying cause of hyperandrogenemia and eventually PCOS. The results will help us understand the causes of PCOS and may lead to preventative treatment.